Dns-servers are meant for translating domain names into ip-addresses. It is required to have at least 2 dns-servers for each domain name. You can find out the correct names of dns-servers from your hosting-provider where you are planning to host the registered domain.
During the process of domain registration you can use the dns-servers given by registrar. In this case domain is registered without hosting it on a server: when entering a website, you will see a page with notice saying that “Domain has been registered”. You can choose a hosting-provider later.